A little while back, a study at the University of Western Ontario found that pregnant women should monitor their heart...

A little while back, a study at the University of Western Ontario found that pregnant women should monitor their heart rate while working out for safety. The study noted that for maximum safety, pregnant women ages 20-29 should work out in a a heart rate zone of 129-160 per minute (bpm). Pregnant women ages 30+ should aim for 128-156 bpm. The study found that women who exceed these bpm levels may experience decreased oxygen levels. A decreased oxygen level for your body, can in turn, decrease the oxygen that gets to your baby's brain. Know your bpm while working out:

Allow your body to guide you. If you can't have a conversation or sing a short song you're likely overdoing it. Also watch for signs of nausea, pain, or dizziness - all of these are signs you need a break.